Connector assembly, thermocouple lead



Oct; 29, 1946. c. w MULLER 2,410,098

CONNECTOR ASSEMBLY, THERMOCOUPLE LEAD Filed April 1, 1945 Patented Oct. 29, 1946 CONNECTOR ASSEMBLY, THERMOCOUPLE LEAD Carl W. Muller, Osborn, Ohio Application April 1, 1943, Serial No. 481,491

(Granted under the act of March 3, 1883, as

2 Claims.

The invention. described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to thermocouple lead connector assembles, such as are useful for making connections through a firewall of an airplane or bulkhead of a ship. Objects of the invention are to provide an improved connector assembly which permits quick connection and disconnection from either side of the firewall or bulkhead; which has a very low resistance, one that is substantially unchanging over a long period of time; which is easy to fabricate and easy to install and remove; and which makes a pressure-tight joint, so that it may be used in so-called supercharged airplane cabins. A further object is to provide a connector assembly employing attachment springs which are not in the thermocouple lead circuit. Other objects will be apparent from the following description of a preferred embodiment of the invention shown in the accompanying drawing, wherein- Fig.1 is an assembly shown in diametric section;

Fig. 2 is an exploded view, partly in section and partly in elevation;

Fig. 3 is a perspective view of the connector assembly with leads connected.

Referring particularly to the drawing, the connector assembly comprises a generally flat body or plate 4 preferably of phenolic molded material or other insulator, with drilled perforations do for studs or screws (not shown) adapted to secure it to one side of a firewall, bulkhead or the like designated at 5. Body 4 has two bores 6 and two annular shoulders or bosses 1 surrounding the bores. Permanently molded in each bore 6 is a bushing or thimble 8, each bushing having an enlarged externally threaded head 9 and a longitudinal axial bore Ill. These bushings or thimbles are preferably made of cadmium plated brass. Shoulders obviate a short circuit through firewall between the bushings.

Bemovably inserted in each bore H) is a socket member having a drilled hole |2 extending longitudinally for about half of its total length and adapted to receive a plug or pin as will be described. If the thermocouple leads (to be described) are of constantan and Armco iron, as is preferred, then socket members II are also respectively of those metals, preferably cadmium plated, in order to preserve continuity of materials in the thermocouple leads. Each socket II also has a longitudinal groove l3 for receivamended April 30, 1928; 370 O. G. 757) ing a flat spring I4, one end of which is secured by a screw l5 threaded into a tapped bore It in the solid portion of the socket. The spring may be of beryllium copper alloy. The free end of spring I4 is bent as at Ma and terminates somewhat short of the end of the socket, entering. a slot I? which is open to drilled hole I2, thus permitting spring end Illa to enter the drilled hole I2 and to be moved outwardly against the tension of the spring. At the opposite end each socket H has a reduced co-axial neck I3 on which a washer i9 is carried, said Washer abut.- ting the end of bushing 8 when the parts are assembled. Extending inwardly ifromthe. free end of the neck is a small drilled bore 28 adapted to receive the end of a lead 2|, also soldered. A brass soldering lug 22, to which washer I9 is soldered, may complete the connection between each lead 2| and the socket H. In all solder connections silver solder is preferably used. A nut 23 is threaded as at 24 upon each head 8 and has a flange 2311 which engages washer l9 to secure each lead 2| yet permit quick detachment thereof. Leads 2| may be connected to an instrument on the panel board.

The other leads 25 (which extend to the engine or other object Whose temperature is to be observed) are soldered to brass soldering lugs 26 each in turn soldered to the end of a pin or plug 21 which may be bent, as shown, Or straight. Each pin or plug has a small machined groove 21a near its rounded extremity 21b and of the proper size to receive the bent spring end Ma. One of the pins 21' is of cadmium plated constantan, the other is of cadmium plated Armco iron, when the same metals are employed for the thermocouple. Both pins are readily insertable in the bores l2 of socket members H, and when inserted fit the bores snugly and are held by frictional engagement of spring end Ma with groove 21a. Disconnection is effected by merely pulling the pins 21 out of the sockets. The dimensions of the two pins and of their respective sockets differ slightly so that it is impossible to couple the leads improperly through the assembly.

When the assembly is to be dismounted, plugs or pins 21 are pulled out at one side of the firewall or bulkhead and the bushings or thimbles are unscrewed from the other side. However, to disconnect the thermocouple lead it is unnecessary to work from both sides of the firewall, although it is quite advantageous to be able to disconnect from either side. The thermocouple lead circuit does not include the springs, which is desirable because a more efiicient and more durable electrical connection is thereby insured; furthermore the readings on the instrument are more accurate. This is especially true when the temperature differential on opposite sides of the firewall is considerable.

Because of the design of the assembly, the contact resistance is very low and does not appreciably change over a long period of time, which is important from the standpoint of dependable instrument readings. Since there are no threads to be cut in the constantan and since machining operations are reduced to a minimum, the various parts of the assembly are easily made, and as already indicated, installation is readily accomplished. When the airplane cabins are sealed for high altitudes (so-called supercharged cabins), no leak will occur through the connector assembly because of the manner in which the described parts are made and fitted together.

Obviously the invention may have many forms neither described nor shown. Instead of constantan and iron two other dissimilar metals or alloys, if efiective in a thermocouple, may be used. Many other changes in details of construction, within the scope of the appended claims, may occur to those skilled in the art.

What is claimed is:

1. An assembly of the character described comprising, in combination, an insulating body having a perforation therein and adapted to be secured to one side of a firewall or bulkhead having an opening,- with the perforation and opening registering; a bushing or thimble secured to the opposite to that on which said insulating body lies; said socket member having a central hole; a

spring secured to said socket member and partially entering said hole; means secured to said socket member at the extreme end thereof and providing an abutment for the adjacent end of the bushing or thimble; a nut threaded on said bushing or thimble and engaging said means to ,secure the socket member immovably within the bushing or thimble; means to electrically connect a lead to the end of the socket member carrying said abutment-providing means; a conducting pin adapted to be manually insertable in the central hole in the socket member to make good electrical connection therewith, and then being frictionally engaged by said spring; and means to electrically connect a lead to said pin.

2. The invention according to claim 1 wherein the insulating body has a boss surrounding the perforation and entering the opening in the firewall or bulkhead to aid in obviating short circuits; the nut being the sole means to hold the socket member and being readily removable from the bushing or thimble to permit manual assembly and disassembly of the conducting parts with and from the parts which support them.

CARL W. MULLER. 

